Such a sealing element is generally known in prior art and is applied from very small to very large dimensions. Particularly for larger dimensions of, for example, an opening to be sealed, a comparatively large prestress of the lip against the part which can move relative to it is frequently required. Examples of this are lengths of pipeline which can move in relation to each other in high pressures lines. To guarantee such a high pressure of the lip against the moving part, various measures have been suggested in the prior art. One suggestion concerned bringing the lips under fluid pressure. Another suggestion comprised the installation of springs to press the lip against the related part. Particularly in cases of high pressure and for relatively small sealing elements, the problem exists of there not being enough space to insert a spring which can provide sufficient closing force.